1. Technical Field
The present invention relates to a projector.
2. Related Art
Previously, a projector including a light source device, a light modulation device that modulates a luminous flux output from the light source device, and a projection optical device that magnifies and projects the modulated luminous flux has been known.
In such a projector, as the light source device, for example, a discharge emission light source device including a light source lamp in which discharge emission is performed between a pair of electrodes and a reflector that aligns and outputs the luminous flux emitted from the light source lamp in a certain direction is often used. In the light source device, the temperature within the light source lamp rises because of heat generation due to light emission and heat convection is caused, a vertical temperature difference is produced within the light source lamp and the gas concentration distribution becomes nonuniform. Accordingly, an arc generated between the pair of electrodes curves upwardly in the vertical direction, the center position of the arc is displaced upwardly in the vertical direction from the center position between the pair of electrodes. At the time of assembly of the light source device, the light source lamp is attached relative to the reflector so that the center position of the arc may be located in a predetermined position of the reflector (e.g., for a parabola reflector, the focal point of the parabola reflector, and for an elliptic reflector, the first focal point of the elliptic reflector).
However, when the projector is compatible between a desktop mount position (a condition in which the projector is mounted on an installation surface of a desk or the like) and a ceiling suspension position (a condition in which the projector is suspended from a ceiling or the like upside down relative to the desktop mount position), top and bottom of the light source device is reversed in the desktop mount position and the ceiling suspension position and the curvature direction of the ark becomes vertically opposite. Accordingly, at the time of assembly of the light source device, in the case where the light source lamp is attached to the reflector as described above in the desktop mount position, when the projector is used in the ceiling suspension position, the center position of the arc is displaced from the predetermined position of the reflector due to inverted curvature of the arc. When the center position of the arc is thus displaced from the predetermined position of the reflector, the optical axis of the luminous flux output from the light source lamp is displaced from the optical axis in design following the optical system provided at the latter part side of the optical path of the light source device. Accordingly, it is impossible to effectively apply the luminous flux output from the light source device to the light modulation device, and the use efficiency of light becomes lower.
Therefore, a projector that is able to improve the use efficiency of light both in the desktop mount position and the ceiling suspension position is proposed (see JP-A-8-314010).
In the projector disclosed in JP-A-8-314010, a lamp unit including a metal halide lamp, a parabola reflector, etc. is formed in a cylindrical shape with an optical axis as a center axis. Further, the inner shape of a lamp unit mounting part in which the lamp unit is mounted is formed in a cylindrical shape corresponding to the outer shape of the lamp unit. The lamp unit is arranged so as to be rotated to 180 degrees with the optical axis as the center axis within the lamp unit mounting part. By the structure, the lamp unit is rotated according to the position of the projector (the desktop mount position and the ceiling suspension position) and the center position of the arc is located in the predetermined position of the reflector.
However, since the projector disclosed in JP-A-8-314010 adopts the structure in which the lamp unit is rotated with the optical axis as the center axis, the operation according to the position of the protector (rotation of the lamp unit) is troublesome.
Further, to smoothly rotate the lamp unit relative to the lamp unit mounting part, a rotation mechanism is required and the light source device is upsized.
Therefore, a technology that is able to improve the use efficiency of light both in the desktop mount position and the ceiling suspension position with a light source device that has a smaller size and a simple structure is desired.